1. Field of the Invention
This invention relates to the manufacture and composition of lubricating oil additives, particularly to molybdenum-containing compositions.
2. Background
Compositions of molybdic acid and oil soluble basic nitrogen containing compounds have been used as lubricating oil additives to control oxidation and wear of engine components. Since their discovery, such complexes have been widely used as engine lubricating oil additives in automotive and diesel crankcase oils and as an additive in some two-cycle oils to prevent valve sticking. Generally, these compounds are added to a detergent package that is added to engine lubricating oils.
Complexes of molybdic acid and oil soluble basic nitrogen containing compounds are normally made with an organic solvent during a molybdenum-containing composition complexation step. The complexation step can be followed by a sulfurization step as disclosed in King et al., U.S. Pat. No. 4,263,152, which is herein incorporated by reference. Related King et al., U.S. Pat. No. 4,272,387, is also incorporated by reference.
After sulfurization, these compositions are extremely dark in color. These compositions are measured at about 5 triple dilute (DDD) using an ASTM D1500 or ASTM D6045 colorimetric test. Since low color lubricating oils are highly desired in the marketplace, these dark compositions can only be used in limited doses because of the impact they have on the finished oil color.
Other related references are: Gatto et al., U.S. Pat. No. 5,650,381, disclose lubricating compositions that contain (a) an active sulfur-free soluble molybdenum compound; and (b) an oil soluble secondary diarylamine; Gatto, U.S. Pat. No. 5,840,672, discloses an antioxidant system for lubricating oil compositions that includes (a) a secondary diarylamine; (b) a sulfurized olefin or sulfurized hindered phenol; and (c) an oil soluble unsulfurized or sulfur-containing molybdenum compound; and Gatto et al., U.S. Pat. No. 6,174,842, disclose lubricants containing (a) molybdenum compounds substantially free of reactive sulfur; (b) phenates; and (c) diarylamines.